A killer remains unpunished 10 years after 21-year-old Orlando Perez was fatally stabbed on a Union City street and bled to death in the arms of a friend.

For Perez’s mother, a decade has not eased the pain.

“I have a broken heart and it will always stay broken,” said Maria Velez, whose son was killed on June 1, 2003 at West and 21st streets. “It was terrible and I’m still not through it.”

Perez was walking from a party to his 23rd Street home with friends at 2:30 a.m. when he got into an argument with someone.

“(Some) kid kept saying, ‘Oh, it’s like that’ (to Perez) and then he went I believe to get his brother,” one of the victim’s friends told The Jersey Journal 10 years ago. “He started waving a knife around. My other friend and I started running. Then I said, ‘Wait a minute, we gotta get Oly.’ ”

By the time the friends reached Perez, it was too late. He’d been stabbed in the side, near his heart, and was bleeding profusely, the friend said.

“I tried to keep him up and apply pressure to the wound, but he wasn’t breathing,” the friend said. “I think he died right in my hands.”

Velez rushed to the scene, but her son had already been taken away. She collapsed in tears.

Hudson County Prosecutor’s Office spokesman Gene Rubino said yesterday that “This is a particularly troubling case because Orlando Perez was only 21 years old when he was killed.”

Rubino said homicide detectives pursued a number of leads and interviewed several witnesses and although no one was charged, they are poised to take the case up again if new clues surface. He also said the case was hampered by heavy rains that presented challenges at the crime scene.

Velez said her son was “happy, funny everybody enjoyed being around him.” He worked at an air-conditioning repair shop, but his mother said he wanted to go to college. She said he told her “he’d be with me the rest of his life.”

Velez is pleading for anyone with knowledge of the stabbing to speak up.

“People should come forward,” she said. “What if this happened to one of your children? You would want people to come forward and say something.”

To the killer, she said, “It’s going to be 10 years. It’s about time you pay for what you have done.”

Anyone with information is asked to call the Hudson County Prosecutor’s Office’s Homicide Squad at (201) 915-1345. Rubino said even a small detail could provide a vital link that can be used in conjunction with new law enforcement technologies and databases.